Dead reckoning is a navigational technique which has been in use for centuries. Dead reckoning calculates the current position of an object based on a previous position of the object in view of the speed and direction travelled from the previous position. Disadvantageously, dead reckoning is subject to significant error, particularly when speed and direction are not measured accurately.
The NAVSTAR (US government owned and operated) GPS constellation comprises a network of 27 Earth orbiting satellites. A complementary space-based network called GLONASS (Russian government owned and operated) consists of an additional 24 satellites. In order to determine the position of an object using GPS/GLONASS, a GPS, GLONASS or combined GPS/GLONASS receiver on the object must determine the location of at least four GPS/GLONASS satellites and the distance between the object and each of the at least four satellites. Disadvantageously, the GPS/GLONASS system cannot be used to calculate position when the GPS/GLONASS receiver does not receive signals from at least four GPS/GLONASS satellites.
The introduction of high-precision global positioning systems (“HPGPS”) to the surface mining industry has resulted in significant improvements in productivity, and is expected to take an essential role as an enabling technology in future efforts to automate mining activities. In a standard system, GPS/GLONASS output is used directly for positioning. However, such systems can be impacted by physical obstacles that prevent the receipt of the satellite signals or as a result of sun spot activity that introduces noise into the signals thus causing them to become intermittently unavailable and/or making them less accurate in the course of normal operation. Therefore, an improved positioning solution that can operate under such poor GPS operational conditions is needed. The apparatus and method of the invention augments GPS with dead reckoning techniques when GPS signals are unavailable or inaccurate.